U.S. patent number 10,145,309 [Application Number 14/818,785] was granted by the patent office on 2018-12-04 for gas turbine fuel control system.
This patent grant is currently assigned to PRATT & WHITNEY CANADA CORP.. The grantee listed for this patent is Pratt & Whitney Canada Corp.. Invention is credited to Joseph H. Brand, Kevin Allan Dooley.
United States Patent |
10,145,309 |
Brand , et al. |
December 4, 2018 |
Gas turbine fuel control system
Abstract
A method of controlling a flow of a fuel mixture of different
types of fuel in a gas turbine engine is described which includes
determining a combustive energy value of an input of the fuel
mixture in the engine, extracting fuel schedule data from a fuel
schedule established for a reference fuel, determining a desired
fuel mixture flow rate by adapting the fuel schedule data to the
fuel mixture based on the combustive energy value, and controlling
a fuel metering device of the engine such that the fuel mixture
flow rate corresponds to the desired fuel mixture flow rate.
Inventors: |
Brand; Joseph H. (Mississauga,
CA), Dooley; Kevin Allan (Toronto, CA) |
Applicant: |
Name |
City |
State |
Country |
Type |
Pratt & Whitney Canada Corp. |
Longueuil |
N/A |
CA |
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Assignee: |
PRATT & WHITNEY CANADA
CORP. (Longueuil, CA)
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Family
ID: |
39111806 |
Appl.
No.: |
14/818,785 |
Filed: |
August 5, 2015 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20160153364 A1 |
Jun 2, 2016 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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13091301 |
Apr 21, 2011 |
9127596 |
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11668762 |
May 31, 2011 |
7950216 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F02C
3/20 (20130101); F02C 9/28 (20130101); F02C
9/40 (20130101); F05D 2270/31 (20130101); F05D
2220/32 (20130101) |
Current International
Class: |
F02C
9/40 (20060101); F02C 9/28 (20060101); F02C
3/20 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0501313 |
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Sep 1992 |
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EP |
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1118857 |
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Jul 2001 |
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EP |
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1500805 |
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Jan 2005 |
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EP |
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61040432 |
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Feb 1986 |
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JP |
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200230944 |
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Jan 2002 |
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JP |
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200436457 |
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Feb 2004 |
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JP |
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8808075 |
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Oct 1998 |
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WO |
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0052315 |
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Sep 2000 |
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WO |
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0140644 |
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Jun 2001 |
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WO |
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Other References
USPTO Non-final Office Action dated Aug. 5, 2010 for U.S. Appl. No.
11/668,762. cited by applicant .
European Search Report issued in Application No. EP08250360.8 dated
Jul. 21, 2011. cited by applicant.
|
Primary Examiner: Sung; Gerald L
Attorney, Agent or Firm: Norton Rose Fulbright Canada
LLP
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATIONS
The present application is a divisional of U.S. patent application
Ser. No. 13/091,301 filed Apr. 21, 2011, which is a divisional of
U.S. patent application Ser. No. 11/668,762 filed Jan. 30, 2007,
now U.S. Pat. No. 7,950,216, the entire content of each of which is
incorporated herein by reference.
Claims
What is claimed is:
1. A method of controlling a flow of a fuel mixture of different
types of fuel in a gas turbine engine, the method comprising:
determining a combustive energy value of an input of the fuel
mixture in the gas turbine engine, by calculating the combustive
energy value from a proportion of each of the types of fuel in the
fuel mixture and from a known combustive energy value of the each
of the types of fuel; extracting fuel schedule data from a fuel
schedule established for a reference fuel; determining a desired
fuel mixture flow rate by adapting the fuel schedule data to the
fuel mixture based on the combustive energy value; and controlling
a fuel metering device of the gas turbine engine such that a fuel
mixture flow rate corresponds to the desired fuel mixture flow
rate.
2. The method as defined in claim 1, wherein the desired fuel
mixture fuel flow rate is a required fuel flow rate upon start up
of the gas turbine engine, the fuel schedule includes start up fuel
data, and the combustive energy value is determined before start up
of the gas turbine engine.
3. The method as defined in claim 2, wherein determining the
combustive energy value includes directly sensing the combustive
energy value.
4. The method as defined in claim 2, further comprising sensing the
proportion the of each of the types of fuel in the fuel
mixture.
5. The method as defined in claim 1, wherein the desired fuel
mixture fuel flow rate is a required fuel flow rate while the gas
turbine engine is lit, the method further includes a step of
sensing temperature and pressure characteristics of the flow of the
fuel mixture and of air within the gas turbine engine to produce
engine sensor data, and wherein the fuel schedule data is extracted
from the fuel schedule based on the engine sensor data.
6. The method as defined in claim 5, further comprising sensing one
or more of a flow rate of the air in the gas turbine engine, a rise
in temperature of the air during combustion, and the fuel mixture
flow rate, and wherein determining the combustive energy value is
performed by calculating the combustive energy from the sensed one
or more of the air flow rate, the rise in temperature and the fuel
mixture flow rate.
7. The method as defined in claim 5, wherein determining the
combustive energy value includes directly sensing the combustive
energy value.
8. The method as defined in claim 5, wherein determining the
combustive energy value includes sensing the proportion of the each
of the types of fuel in the fuel mixture, and calculating the
combustive energy value from the sensed proportion and from the
combustive energy value of each of the types of fuel.
9. The method as defined in claim 1, further comprising determining
at least one equivalent characteristic of the reference fuel
corresponding to the combustive energy value, and displaying the at
least one equivalent characteristic.
10. The method as defined in claim 9, wherein the at least one
equivalent characteristic of the reference fuel includes an
equivalent mass flow of the reference fuel.
11. The method as defined in claim 1 wherein the combustive energy
value is the lower heating value.
Description
TECHNICAL FIELD
The invention relates generally to gas turbine engines and, more
particularly, to an improved fuel control system thereof.
BACKGROUND
Gas turbine engines are generally adapted to be used with a single
type of jet fuel, for example JP4 jet fuel. As such, use of a
different fuel, for example ethanol, in these engines can be
detrimental to the engines' performances, as the fuel flow in the
engine is usually controlled through a series of fuel schedules
established for a specific type of fuel and as such not adapted for
other types of fuel of mixtures thereof.
With the rise of fuel costs, some areas of the world may choose to
use Ethanol or mixtures of Ethanol in Jet fuel, accepting a reduced
flight range for the cost savings. However, refueling with a fuel
that may be different from the fuel already contained in the tank
can cause the precise equivalent content of the fuel tanks to be
unknown. A pilot who is confused as to the exact type of fuel
contained in the fuel tanks can be mistaken upon calculation of the
range of the aircraft. This can be hazardous, especially in cases
where the range is overestimated.
Accordingly, there is a need to provide an improved fuel control
system and/or method for a gas turbine engine.
SUMMARY
There is therefore provided a method of controlling a flow of a
fuel mixture of different types of fuel in a gas turbine engine,
the method comprising: determining a combustive energy value of an
input of the fuel mixture in the engine; extracting fuel schedule
data from a fuel schedule established for a reference fuel;
determining a desired fuel mixture flow rate by adapting the fuel
schedule data to the fuel mixture based on the combustive energy
value; and controlling a fuel metering device of the engine such
that the fuel mixture flow rate corresponds to the desired fuel
mixture flow rate.
There is alternately provided a method of controlling a flow of a
fuel in a gas turbine engine comprising sensing at least one
characteristic of the flow, determining a combustive energy value
of the fuel based on the at least one characteristic, determining a
desired fuel flow rate at least based on the combustive energy
value, and controlling a fuel metering device of the engine to
obtain the desired fuel flow rate.
There is alternately provided a method of monitoring a flow of a
fuel in a gas turbine engine comprising sensing at least one
characteristic of the flow, determining a combustive energy value
of the fuel based on the at least one characteristic, determining
at least one equivalent characteristic of a reference fuel
corresponding to the combustive energy value, and displaying the at
least one equivalent characteristic.
There is alternately provided a fuel control system for a gas
turbine engine comprising at least one sensor determining at least
one characteristic of a fuel flow in the engine, a combustive
energy value evaluator determining a combustive energy value of the
fuel from the at least one characteristic, a fuel metering device
metering a fuel flow rate in the engine, and a controller
calculating a desired flow rate based at least on the combustive
energy value and controlling the fuel metering device such that the
fuel flow rate corresponds to the desired flow rate.
There is alternately provided a method of controlling a flow of a
fuel mixture of different types of fuel in a gas turbine engine,
the method comprising: determining a combustive energy value of an
input of the fuel mixture in the engine; extracting fuel schedule
data from a fuel schedule established for a reference fuel;
determining a desired fuel mixture flow rate by adapting the fuel
schedule data to the fuel mixture based on the combustive energy
value; and controlling a fuel metering device of the engine such
that the fuel mixture flow rate corresponds to the desired fuel
mixture flow rate.
There is alternately provided a system for monitoring a flow of a
fuel mixture of different types of fuel in a gas turbine engine,
the system comprising: a unit determining a combustive energy value
of the fuel mixture in the engine; a controller determining at
least one equivalent characteristic of a reference fuel
corresponding to the combustive energy value of the fuel mixture;
and a display unit displaying the at least one equivalent
characteristic.
There is alternately provided a control system for a fuel mixture
of different types of fuel in a gas turbine engine, the system
comprising: a unit determining a combustive energy value of an
input of the fuel mixture in the engine; and a controller
extracting fuel schedule data from a fuel schedule established for
a reference fuel, calculating a desired flow rate of the fuel
mixture by adapting the fuel schedule data to the fuel mixture
based on the combustive energy value, and outputting a signal
adapted to control a fuel metering device of the engine such as to
conform a fuel mixture flow rate to the desired flow rate.
Further details of these and other aspects of the present invention
will be apparent from the detailed description and figures included
below.
DESCRIPTION OF THE DRAWINGS
Reference is now made to the accompanying figures depicting aspects
of the present invention, in which:
FIG. 1 is a schematic, cross-sectional view of a gas turbine
engine; and
FIG. 2 is a schematic representation of a fuel control system
according to a particular embodiment of the present invention.
DETAILED DESCRIPTION
FIG. 1 illustrates a gas turbine engine 10 of a type preferably
provided for use in subsonic flight, generally comprising in serial
flow communication a fan 12 through which ambient air is propelled,
a compressor section 14 for pressurizing the air, a combustion
section 16 in which the compressed air is mixed with fuel atomized
into a combustion chamber 17 by a fuel injection system 20, the
mixture being subsequently ignited for generating hot combustion
gases before passing through a turbine section 18 for extracting
energy from the combustion gases.
Referring to FIG. 2, the flow of fuel to the fuel injection system
20 is controlled by a fuel control system 22. The fuel control
system 22 includes a fuel metering device 24 metering the fuel
reaching the fuel injection system 20. The fuel metering device 24
is electrically controlled in a precise and predictable manner by a
controller 26. In a particular embodiment, the controller 26 is
part of the electrical and electronic engine control (EEC) (not
shown) of the engine 10.
The controller 26 generally receives data from various engine
sensors 28. This data includes pressure and temperatures at various
points of a flow path of the engine 10, as well as fuel mass flow.
Based on this data, the controller 26 refers to fuel schedules 30
both upon start-up of the engine 10 and once the engine 10 is lit,
to determine a desired fuel flow and control the fuel metering
device 24 accordingly. The fuel schedules 30 generally determine
ranges for the desired fuel flow for one type of reference fuel,
for example JP4 jet fuel. The controller 26 also sends data to
other systems for calculations and display on a display unit 32
which displays the received data, for example in the cabin of the
aircraft (not shown). Such data may include, for example, the fuel
mass flow, quantity of fuel burned and remaining quantity of fuel.
The controller 26 further controls an ignition system 34 of the
engine 10 upon start-up.
In order for the engine 10 to be able to function with fuel such as
ethanol or an unknown mixture of ethanol and jet fuel, the fuel
control system 22 includes a fuel mixture sensor 36 which is in
line with the fuel injection system 20 (shown in FIG. 1) and which
determines the general mixture between ethanol and jet fuel
contained in the fuel supplied to the engine 10. The fuel mixture
sensor 36 thus sends data on the composition of the mixture to the
controller 26. The fuel control system 22 also includes an energy
value evaluator 38 which determines an energy value of the fuel
mixture, either directly by measurement or by reference to tables
based on mixture ratios. In a particular embodiment, the energy
value evaluator 38 determines the lower heating value (LHV) of the
fuel mixture. The fuel control system 22 further includes a
reference fuel table 40, which contains characteristics of the
reference fuel in relation to the corresponding energy value. Such
characteristics may include for example fuel mass flow required for
various mixtures such that a specific LHV flow rate can be provided
to the combustion system.
In use, at start-up of the engine 10, the controller 26 actuates
the fuel mixture sensor 36 through a signal 50 and the fuel mixture
sensor 36 determines the composition of the fuel supplied to the
engine 10, i.e. the proportion of ethanol and jet fuel in the fuel.
Alternately, the LHV of the fuel may be measured directly with an
in line LHV sensor, providing directly the information desired. The
fuel mixture sensor 36 then sends corresponding proportion data 52
to the controller 26. The controller 26 also actuates engine
sensors 28 through a signal 54 and receives sensor data 56
therefrom, which includes for example the air mass flow and the
pressure and temperature in the flow path at the end of the
compressor section 14. In the case where a direct LHV sensor is
implemented, the fuel mass flow required for a given engine inlet
air mass flow can be directly calculated by the engine control
system
The controller 26 then sends data 58 to the energy value evaluator
38, the data 58 including the proportion of ethanol and jet fuel in
the fuel and relevant sensor data. The energy value evaluator 38
determines the instantaneous LHV of the fuel mixture, for example
from a database correlating the relevant sensor data and fuel
proportion to the LHV. A given fuel mass flow of a particular fuel
corresponds to a given amount of fuel energy (LHV*mass flow) that
this fuel provides to the combustor. For example, the LHV of JP4
jet fuel is roughly about 18,000 BTU (British Thermal Units) per
pound mass of the fuel, and thus at an exemplary fuel consumption
rate of about 200 pounds of fuel flow per hour, the LHV input value
to the combustor would be about 3.6 million BTU per hour. For the
same engine condition using ethanol, for example, 3.6 million BTU
per hour would still be required, however since ethanol has only
about 60% of the energy content compared to JP4, the fuel mass flow
rate of ethanol would need to be about 1.666 times as high as that
for JP4, which in this example corresponds to about 366 pound of
ethanol per hour. Once the instantaneous LHV of the fuel mixture
has been determined by the energy value evaluator 38, the energy
value evaluator 38 then sends the LHV 60 to the controller 26.
Alternately, the fuel mixture sensor 36 can directly determine the
LHV as a means to determine the proportion of ethanol and jet fuel
in the fuel, and in this case the data 52 sent by the fuel mixture
sensor 36 to the controller 26 includes the LHV, and the energy
value evaluator 38 is used during start-up. However, the proportion
of ethanol to jet fuel need not be known if the LHV is measured
direction as described above. In one embodiment, the LHV is
determined specifically for the start up flow settings, as once the
engine is running the LHV of the fuel can be determined using the
measured temperatures and air mass flow rates of the engine. Thus,
the specifically measured LHV values may not necessarily be needed
once the engine has been started. By using the engine air mass
flow, the air inlet and outlet temperatures, and the fuel mass flow
rate, the instantaneous LVH values in the fuel can be determined.
The plurality of instantaneous calculated LVH values are then held
in a temporary memory register, and used by the control system to
allow smooth control of the engine fuel flow for both steady state
running and transient running. The value of LHV may be calculated
once the engine is running every second or two, or alternately more
or less often. Regardless, the general approach of establishing the
LHV of the fuel before start is nonetheless desirable such that
correct start-up flow rates can be set without fear of overheating
during start or failing to start properly. The LHV values can then
be periodically determined, from the engine parameters as
described. The LHV before start is determined by establishing the
mixture and then using a table or calculation method to determine
LHV and then set the start flow based on this. Alternately,
however, the LHV may be sensed directly, and the start fuel flow
can then be set based on a direct knowledge of the LHV.
Regardless of how the LHV is determined, the controller 26 accesses
the fuel schedules 30, as shown at 62, based on the sensor data,
and retrieves corresponding fuel schedule data 64 related to
start-up. The controller 26 then uses the LHV or the equivalent LHV
and fuel proportions as described above, to adapt the fuel schedule
data to the actual fuel used in the engine in order to determine a
desired fuel flow and ignition settings.
The BTU input requirement to the engine is always predetermined by
engine designers. The fuel flow rate is measured and controlled,
and given that the LHV specifications of aircraft fuel must by
regulations be within a specific narrow range, the need for LHV
measurement or determination by the engine system never existed in
the past.
The controller 26 then actuates the fuel metering device 24 through
a signal 66 corresponding to the desired fuel flow, optionally
receiving feedback 68 from the device 24. The controller 26 also
actuates the ignition system 34 through a signal 70 corresponding
to the ignition settings, optionally receiving a feedback 72 from
the ignition system 34.
Once the engine 10 is lit, the controller 26 still receives the
sensor data 56 from the engine sensors 28, which includes for
example, fuel mass flow, air mass flow, temperature in the flow
path at the end of the combustion section 16, etc. The controller
26 sends this data to the energy value evaluator 38, as shown at
58, which determines the corresponding instantaneous LHV of the
fuel mixture. The LHV of the fuel input can be calculated by
knowing the air mass flow and the temperature rise of that air mass
when combustion occurs. This then provides the total BTU/hour of
energy released by the fuel, and thus dividing by the fuel flow
rate (in pounds per hour, for example) will provide the energy in
the fuel in BTU per pound.
The energy value evaluator 38 sends the LHV 60 to the controller
26, which again accesses the fuel schedules 30, as shown at 62,
based on the sensor data, and retrieves corresponding fuel schedule
data 64 related to lit operation. The controller 26 uses the LHV to
adapt the fuel schedule data to the actual fuel used in the engine
in order to determine a desired fuel flow. As during start-up, the
controller 26 then actuates the fuel metering device 24 through the
signal 66 corresponding to the desired fuel flow.
The controller 26 thus regulates the operation of the fuel metering
device 24 based on the LHV determined by the energy value evaluator
38. As the energy value evaluator 38 constantly calculates the LHV
during the operation of the engine 10, the controller 26 reacts to
variations in composition of the fuel and adjusts the fuel metering
device 24 accordingly to optimize performance of the engine 10.
While the engine 10 is running, the controller 26 also accesses the
reference fuel table 40, as shown at 74, and retrieves at least one
reference characteristic 76 of the reference fuel corresponding to
the LHV of the actual fuel used. For example, the controller 26
determines the corresponding mass flow of the reference fuel which
would have been required to obtain the LHV obtained with the actual
fuel and determined by the energy value evaluator 38. Based on the
history of the operation of the engine 10, the controller 26 can
also calculate an equivalent quantity of reference fuel burned. The
controller 26 then sends normalized data 78, i.e. the equivalent
characteristics of the reference fuel corresponding to the actual
LHV of the fuel used, to the display unit 32, which displays it for
the pilot. As such, the pilot can see the fuel data normalized to a
reference fuel, i.e. as if the reference fuel was being used in the
engine 10. The display unit 32 also provides the pilot with an
indication of the real fuel quantity being used versus how much
real fuel quantity is present in the fuel tanks. Accordingly, the
actual fuel mass flow is measured and used for any information
provided to the pilot. For example the mass flow and quantity of
reference fuel corresponding to the actual operation of the engine
can be displayed. Using this normalized data, standard calculations
for range of the aircraft can be done by the pilot regardless if
he/she is aware of the real composition of the fuel being used in
the engine 10, thus eliminating errors due to confusion of fuel
type used. This includes corrections of SG (specific gravity) which
is also one of the parameters sensed, as the fuel level in the fuel
tank may not be representative in terms of available range from one
fuel to another, even if the BTU per Lb is known (i.e. the volume
of fuel is what is provided by a level measurement device not the
mass of fuel in the tank).
As such, the fuel control system 22 provides for control of the
fuel metering device 24 adapted to a fuel which is a mixture of two
different fuels with variable proportions, as well as normalisation
of the operation of the engine to a known, reference fuel to
facilitate operation of the engine. As such, the pilot can use the
normalized data displayed to perform standard calculations such as
range calculation without the need to verify the exact composition
of the fuel.
Although in the preferred embodiment, the energy value used is the
lower heating value or LHV, it is understood that other energy
values can similarly be used. The above description is meant to be
exemplary only, and one skilled in the art will recognize that
changes may be made to the embodiments described without department
from the scope of the invention disclosed. For example, the fuel
control system 22 can be used with other configurations of gas
turbine engines and with other types of engine. The reference fuel
used can be any appropriate type of fuel. Still other modifications
which fall within the scope of the present invention will be
apparent to those skilled in the art, in light of a review of this
disclosure, and such modifications are intended to fall within the
appended claims.
* * * * *